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Old 11-06-2013, 18:27   #1
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thru hull & valve question

I am replacing a couple of 27yo gate valves that are on some thru hulls with quarter turn bronze ball valves and was wondering what if anything should I put on the threads when i screw on the valves ? also if I need to add any elbows or nipples, is it ok to use brass ones or do they have to be bronze as well? OK thanks ! ! ! AHHHhhhh got to love retired life aboard
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Old 11-06-2013, 18:36   #2
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Re: thru hull & valve question

Never use brass below the waterline. Brass will suffer from dezincification in contact with salt water. Brass can corrode even more quickly if your boat or your marina has stray current issues which unfortunately are not uncommon.

It is also critical that you match the threads of the throughull to those of the valve. Many throughulls are NPS (straight thread and many valves are NPT (tapered thread. Be sure you know what you are dealing with.
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Old 11-06-2013, 18:41   #3
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Re: thru hull & valve question

No brass for thruhulls...ever.

Use 3M 4200 as your sealant.
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Old 11-06-2013, 18:41   #4
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Re: thru hull & valve question

Got it, bronze only ! Thanks and as for the thread part I mean should i put any type of sealant or thread dope etc on the threads
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Old 11-06-2013, 18:42   #5
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Re: thru hull & valve question

3M 4200
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Old 11-06-2013, 20:14   #6
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Re: thru hull & valve question

You might take the opportunity to install real flanged seacocks. They are a lot stronger than ball valves screwed directly onto a thru-hull fitting.

Groco Full-Flow Flanged Ball-Type Seacocks FBV750-2000

Another option is to use a Groco flanged adapter. It solves the problem of mis-matched threads and gives the support of a flange.

Groco Flanged Adapter IBVF
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Old 11-06-2013, 20:22   #7
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Re: thru hull & valve question

Quote:
Originally Posted by firedreamer View Post
also if I need to add any elbows or nipples, is it ok to use brass ones or do they have to be bronze as well?
Bronze nipples are very hard to find. I believe nipples made out of red brass, also known as 85-5-5-5 brass or gunmetal, are OK.
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Old 11-06-2013, 20:27   #8
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Re: thru hull & valve question

David, why 4200? 3M doesn't market it as a thread sealant. I don't see why it wouldn't work but it seems an odd choice when there are so many products designed as thread sealants.

My favorite thread sealant is Leak Lock because it can be used on almost all materials and seals against almost all chemicals (it doesn't like alcohol). I use something else on my still.

Leak Lock by Highside INC.
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Old 11-06-2013, 20:51   #9
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Re: thru hull & valve question

Hey Firedreamer, I strongly suggest you follow Hop Car's advice. I would go with the full seacocks flanged with valve. I use teflon pipe dope on the threads, not tape, dope comes in a can with a brush attatched to the lid. I have probably done close to a hundred of them. The purpose of the flange is to give extra strength in case someone steps on it. If you replace them like this, you will have a setup that will outlast you or the boat. Also, good for resale.
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Old 11-06-2013, 21:25   #10
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Re: thru hull & valve question

Ziggy is correct. In fact almost all of the "bronze" pipe fittings you will find in a marine store are 85-5-5-5 and that's ok. It is a very corrosion resistant metal. The zinc amount is so low that dezincification is not an issue.

What you want to avoid are yellow brasses which can have anywhere from 20 to 40% zinc.
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Old 11-06-2013, 21:59   #11
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Re: thru hull & valve question

I replaced a seacock/thru-hull with a Groco flanged adapter using info from this site, Compass Marine "How To" Articles Photo Gallery by Compass Marine at pbase.com

Everything seemed to turn out well.
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Old 11-06-2013, 22:25   #12
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Re: thru hull & valve question

Go for 'Tru-design' or 'Marelon' if you wish, i did and they are very good.

Also my boat had the same valves that you mention fitted and i've removed them after 5 years immersion and they are fine.....

Loctite make good pipe sealants.

Cheers
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